Adaptive Method for High Data Rate Communication In Wells

ABSTRACT

Apparatus for downhole transmission and reception of data in an oil or gas well comprises a downhole signal transceiver adapted to receive data from a signal generator and transmit the signal through the well and an elongate member with an axis, located in the wellbore; wherein the signal is transmitted by the transceiver, predominantly axially along the elongate member.

TECHNICAL FIELD

This invention relates to an apparatus and method for downholetransmission of signals.

It is normally desirable to measure various parameters during drillingand subsequent testing of an oil or gas well, for example pressure,temperature, formation data, and wellbore trajectory at or near thebottom hole assembly (BHA) and drill bit and along the well bore, and torelay these measurements back to the surface where the drillingoperation can be controlled. During drilling operations, the weight onbit and rate of rotation of the drill string are two typical parametersthat are controlled at the surface in order to affect the rate ofpenetration of the drill bit through the formation. For example, it isdesirable for the drilling engineer controlling the drilling operationat the surface to know when the drill bit is experiencing aggressivelocal conditions as it cuts into the formation, such as hightemperatures, pressures, or resistance to penetration, so that they canadjust for example the rate of rotation, the weight on bit, and the rateof supply of drilling fluid to the bit in order to avoid driving the bitbeyond it's normal operational parameters and thereby reducing the riskof bit failure, which would require expensive and time consumingintervention. This Measurement While Drilling (MWD) is well known in theart and various mechanisms have evolved for gathering data at the bitand transmitting these data back to the driller at the surface. Thepresent invention relates particularly to novel aspects of thetransmission of signals or data (such as Measurement While Drilling,Logging While Drilling, Seismic While Drilling, and Formation EvaluationWhile Drilling) gathered at the bit or at points along the drill pipe orwell-bore and transmitted to the surface, and also to the transmissionof signals from the surface down the well towards the bit in order tocontrol or operate any downhole tools or devices.

According to the present invention there is provided apparatus fordownhole transmission and reception of data as claimed in theaccompanying claims.

Also according to the present invention there is provided a method ofdownhole transmission of data as claimed in the accompanying claims.

Also according to the present invention there is provided apparatuscomprising a wireless network formed by the interaction of transceivernodes as claimed in the accompanying claims.

Also according to the present invention there is provided apparatuscomprising high data rate electrical signal pathways as claimed in theaccompanying claims.

Also according to the invention there is provided apparatus for downholetransmission and reception of data in an oil or gas well, the apparatuscomprising a downhole signal transceiver adapted to receive data from asignal generator and transmit the signal through the well; and anelongate member with an axis, located in the wellbore; wherein thesignal is transmitted by the transceiver, predominantly axially alongthe elongate member. The invention also provides a method of downholetransmission and reception of data in an oil or gas well, the methodcomprising providing a downhole signal transceiver adapted to receivedata from (a) signal generator and transmit the signal through the well;providing an elongate member with an axis, extending through thewellbore; and transmitting the signal from the transceiver along theelongate member.

Optionally more than one downhole transceiver is provided, e.g. 2, 3, 4,or more transceivers are linked optionally in series as nodes along theelongate members Optionally the signals transmitted comprise signalsfrom the or each transceiver, and one or more sensors in the well.Typically the signal presented at the transceiver nodes and at theelongate members is a radio frequency (RF) signal and the elongatemember incorporates a conductor comprising a conductive element ormaterial which can act as an effective carrier or transmitter of RFsignals. Typically the signal conductor can comprise a metal and canoptionally comprise a metallic strip or component optimised in itselectrical or material properties or dimensions to carry the RF signal.Typically the signal is transmitted along the length of the elongatemember. The conductor can optionally be optimised in its effectivenessof carrying or transmitting RF signals by variations to its electricalimpedance, through changes to its material composition or morphologyand/or changes to its physical arrangements such as width, thickness,length and separation from adjacent surfaces, which can influence itselectrical impedance and electrical resistance and efficiency atcarrying RF signals. Optionally, the electrical conductor will beelectrically insulated from the environment by resting withinelectrically-insulating materials optimised for the RF signals beingtransmitted. Optionally, the electrical insulating materials can becoated with further protective layers which may be electricallyconducting.

Typically the signal can be transmitted wirelessly across theconnections between elongate members, and optionally across membersthemselves, by which is meant that the signal can be transmitted acrossregions of space and distances in which no traditional wires ortraditional electrical conductors are in intimate contact with eachother.

Typically the elongate member comprises a downhole tubular, typicallywith a hollow bore through the tubular. Typically the downhole elongatemember is adapted to connect into a string of elongate members.Typically the string is a string of tubulars configured to provide afluid pathway through the bore of the string. The tubular can optionallybe formed and arranged in separate lengths or sections which areconnected together as the string is being made up, as is known in theart. For this purpose, the tubular can optionally have end connectionsadapted to interconnect to form the string. Box and pin arrangementsthat are well known in the art are suitable for this purpose, althoughother connection types are within the scope of the invention.

Typically end connectors adapted to interconnect adjacent stands oftubular can have radial lips or other projections extending radiallyoutward from the nominal outer diameter of the tubular as is known inthe art.

Typically the apparatus comprises a series of signal conductors adaptedto provide a signal pathway for passage of the signal transmitted fromthe transceiver nodes through the well. The signal conductors aretypically mounted on the surface of the elongate members.

Typically the signal conductor has a lower electrical transmission lossto transmission of the signal than the elongate member or thesurrounding fluid medium, thereby increasing the efficiency oftransmission between transceivers. Typically the signal conductorcomprises a network of strips of electrically conductive materialprovided in a layer Typically the layer can extend substantiallycircumferentially around the outer or inner surface of the tubular,although in certain embodiments, the signal conductor can beincorporated within the wall of the tubular instead of beingsubsequently applied to it. Typically the signal conductor can extendaxially along the elongate member, as well as circumferentially, so thatthe signal carried by the signal conductor is transmitted along theconductor and along the axial length of the elongate member. Typicallythe signal conductor is formed substantially circumferentially aroundthe elongate member. For example, the signal conductor can optionallycover a substantial portion of the circumference of the elongate member.Alternatively, the signal conductor can cover a small or large part ofthe circumference of the elongate member, e.g. any proportion of thecircumferential distance around the elongate member.

Optionally the signal conductor can extend between the two ends of anelongate member, and in some embodiments of the invention, the signalconductor can optionally terminate before the end of the section oftubular, and does not necessarily require a continuous electricalconnection to be made between the signal conductor on one section ofelongate member, and the signal conductor on the adjacent sections. Incertain embodiments the signal conductor can comprise one or moreaxially-aligned strips. Typically more than one axial strip is providedand adjacent axially-aligned strips can optionally be parallel to oneanother, so that they extend parallel to the axis along the length ofthe elongate member. In some embodiments, it may be desirable to havenon-parallel alignments of the strips, to provide for example, usefulgeometries to avoid certain damage mechanisms at certain positions alongthe elongate member. In certain embodiments, the signal conductor can beof uniform dimensions of width and thickness along the length of thesignal conductor. In certain embodiments, the width and thickness of thesignal conductor may vary along its length or at its ends as required byoptimum transmission and reception of the signals. In certainembodiments, the physical dimensions (width and thickness) of theinsulating layers can be uniform along the length of the elongatemember. In certain embodiments the physical dimensions of the insulatinglayers along the length of the elongate member may vary, as required byoptimum transmission and reception of the signals.

The signal conductor can optionally form a mesh of wires or strands ofmetal. The wires or strands in the mesh can optionally have physicalinterconnections between different strands of wire, and these can beregular or irregular. Optionally, wires or strands in the mesh caninstead or additionally be pressed into contact with adjacent wires,without structural connections between them. In either event, the meshtypically comprises numerous electrical interconnections betweenadjacent strands of metal in the signal conductor (which can be formedfrom physical connections resisting disconnection of the wires, or fromsimple contact between adjacent wires that are touching, without anyother kind of physical inter-connection) so that the signal pathwayalong the axial length of the tubular through the conductor has manydifferent optional routes to travel typically in a predominantly axialdirection, through the conductor. The signal conductor can optionally bea mesh such as a sheet or layer of woven material that is optionallyplanar, and optionally of a generally uniform thickness, which cantypically be wrapped around the outer surface of the tubular. The meshcan be regular or irregular in pattern and strands of individual wiremaking up the mesh can be continuous or non-continuous. The mesh can bewrapped around or adhered to the outer surface of the tubular in a flatsheet or can be formed in a sleeve with a bore which is passed over thetubular and therefore fixed to its exposed surface.

In typical embodiments of the invention, the signal conductor comprisesan electrically conductive metal Optionally the tubular member andconductor are formed from different metals and the conductor istypically inherently adapted to transmit the signal with a lower signalloss and with a higher data transmission rate than the tubular.Preferred metals for the conductor are those that are electricallyconductive and include various states and qualities of copper, or forexample, zinc, aluminium, iron, steel, gold, platinum and silver andtheir alloys. Typically, the tubular has a coating that spaces (e.g.radially spaces) the signal conductor from the material of the tubular.

Typically the coating is an electrically isolating coating thatelectrically isolates the signal conductor from the elongate member.Optionally the signal conductor can be covered by the coating, so thatthe signal conductor is optionally embedded within the layer of coatingand located between the surface of the coating and the inner bore of thetubular. The signal conductor can be formed integrally with the coatingor in a separate process. The signal conductor can be moulded, sprayedor cast or otherwise applied (by various different methods known to theskilled person) inside the electrically-isolating coating, and thecoating and the signal conductor can optionally be applied around thefull circumference as an integral wrap (or in separate wraps) around theouter or inner exposed surface of the tubular.

Typically, the coating material has high resistivity to minimise theunwanted flow of electrical charge and has properties beneficial to thetransmission of electrical signals and RF signals such as dielectricloss and dielectric constant optimised for the geometry and the RFsignals.

Typically the coating comprises an insulating material (e.g. anelectrical insulator) and typically the coating isolates the signalconductor from the tubular and from the local environment. Ceramicmaterials such as Alumina, Yttria-Stabilised Zirconia, Zirconia, Silica,combinations thereof or similar materials are useful in this regard forapplication to oil well drill pipe, production pipe or casing pipe, dueto the temperature-resistant and wear resistant properties. For otherless demanding applications, less hardy electrical insulators such asplastics, polymers, epoxies, paints and lacquers may be considered.

The tubular (elongate member?) can optionally have additional, one ormore, abrasion resistant materials on its exposed (e.g. outer) surfaceadapted to protect the signal conductor and other insulating coatingsagainst abrasive damage, impacts, wear and erosion etc. The additionalabrasion resistant material can optionally comprise the protectivecoating, and/or can be applied separately to the exposed (e.g. outer)surface of the existing conductor or coating. The additional abrasionresistant material typically comprises a hard material such as aluminaor tungsten carbide, or a similar material that resists impact, wear anderosion on the exposed surface. The outermost abrasion resistantmaterial is typically provided on the exposed surfaces of the tubularlikely to receive greatest wear or impact. Optionally, this abrasionresistant material can also have electrical properties that will enhancethe transmission of electrical signals and RF signals, rendering theouter-most abrasion-resistant material to be optionally electricallyresistive or electrically conducting, as dictated by the electricallosses that are allowable for a specific application or part of theelongate member.

Embodiments of the invention therefore typically provide a series ofsuccessive signal conductors on each adjacent section of tubular whichprovide a low loss path for the transmission of the signals from thesensor at one end of the string of tubulars and along the string to thesignal collection point at the other. In for example drillingoperations, the sensor can typically be at the bottom end of the welladjacent to the bit, and the signal collection point can typically be atthe surface, so that the signal travels up the string from the bit tothe surface. However, in some embodiments, the signal can travel fromthe surface to a device or other signal collection point at intermediatelocations in the well, for example in the down hole tool located in thestring, for example at the bottom hole assembly.

Optionally the signal conductor extends axially from one point adjacentto one end of the tubular towards the other end. Optionally each sectionof tubular between end connections has one or more respectivetransceiver nodes adapted to receive a signal from an adjacent sectionof tubular and retransmit the signal along the next section of tubular.In some embodiments it is not necessary for each section of tubular oreach section of signal conductor to have a corresponding separatetransceiver node on each section, and transceiver nodes can be providedon the string at locations separated spatially in accordance with thedesired strength of the signal and transmission rates of the signal.

Typically each transceiver node transmits the signal wirelessly,typically as radio frequency signals, without requiring a directelectrical connection to the signal conductor. The transceiver nodes aretypically located close to or applied radially over the signal conductor(but typically electrically insulated there from by the coating or theabrasion resistant layer) so that the RF signal transmitted by thetransceiver node is picked up wirelessly by the signal conductor andtransmitted along the signal pathway provided by the signal conductorfrom one end of the section of tubular to the other. At the other end ofthe tubular, the transceiver node on the next section of tubular (or thesignal conductor on the next section of tubular) picks up thetransmitted signal from the end of the adjacent tubular section andtransmits it along the signal conductor located on the next tubularsection. In this way, each section of tubular receives and optionallyboosts the signal and sends it axially along the length of the string.

Typically the transceiver nodes comprise collars or annular housingsthat are applied to the outer surface of the tubular, typically over theouter surface of the signal conductor. Alternatively, the transceivernode can be incorporated as a sub assembly terminating in similarconnections to the elongate members and inserted between two suchmembers if desired. In certain embodiments, the transceiver can beincorporated within the wall of the tubular, as typified in aside-pocket mandrel, but it is often useful to be able to retrofitexisting sections of tubular with embodiments of the invention, soexternally-applied and wrap-around transceiver nodes are considered tobe the most useful embodiments within the scope of the invention.Typically, the transceiver nodes can comprise attachment devices toconnect physically to the tubular, such as clamps, straps, frictionreducers, annular spacers etc., arranged optionally, as annular‘split-rings’ that can be connected to the elongate members prior totheir insertion into a well, for example, at the rig floor.

Typically the transceiver node can incorporate one or more of a powersupply, for example a battery, voltage regulation, any number of radiofrequency transmitters operating at various frequencies, any number ofradio frequency receivers operating at various frequencies, associatedamplifiers, modulators, microprocessors, signal conditioning andprocessor devices and optionally one or more sensors adapted to reportvibration, temperature, pressure, and other conditions in the well.Embodiments of the invention provide two-way high data ratecommunication systems. The combination of transceiver nodes plus thenetwork of electrical interconnections in the signal conductor typicallyforms an adaptive network, and the signal being transmitted along thesystem finds the path of least electrical loss to the transmission andthis leads to more reliable, effective and faster data transmission, andminimises energy consumption during the transmission process.Optionally, as the conductor does not require full electrical continuityalong its length between the transceiver nodes, damage to any particularsection of coating or conductor or the loss of an individual transceivernode does not result in loss of the data, or loss of ability to transmitalong the signal path within the energy capacity of the system. Theelectrical conductor geometries and network of interconnections alsoprovides for redundancy in the pathway of the conductor in the event ofcomponent failures at any point of the elongate member.

Embodiments of the invention can typically achieve higher datatransmission rates than was previously possible as a result. Typicalexcitation frequencies are up to Giga Hertz enabling data transmissionrates from bits per second through to Megabits per second or more. Eachdata set transmitted in the signal is typically identified by a uniquemarker (typically encoded in the RF signal) so that the source andsignificance of each data reading can be differentiated at surface. Thistagging of data sets is typically applied to each of the multiple datatypes generating from the BHA and from each sensor in the varioustransceiver nodes taking readings along the well bore path to thesurface. Additionally the transceiver nodes themselves typically eachhave a unique marker (typically encoded in the RF signal) to distinguisheach node from any other node, and allow identification of each nodefrom the surface. Corruption of the data transmitted along the elongatemembers can optionally be detected using techniques well known in theart such as parity checks. To minimise the need for retransmission ofdata when only partial corruption of the data has occurred, techniqueswell known in the art such as Forward Error Correction may be optionallyimplemented.

To minimise the effect of commonly occurring radio frequencycommunication problems such as interference or multipath cancellation,techniques well known in the art such as spread spectrum, errorcorrection and encoding techniques such as Manchester encoding mayoptionally be implemented in the embodiment.

The transceiver nodes may be managed by a proactive link-state routingprotocol, which uses beaconing, and topology control (TC) messages todiscover and then disseminate link state information throughout the‘ad-hoc’ network. Individual transceiver nodes use this topologyinformation to compute next hop destinations for all nodes in thenetwork using the most energy-effective hop forwarding paths.Optionally, as each packet of data is received at a transceiver node, itwill, as described above, typically confirm receipt back to theoriginating transceiver node via ‘hand shake’ protocols that are knownin the art. If a transmitting node fails to receive a confirmation ‘handshake’ from the node to which it was previously transmitting, it canoptionally be programmed to change the transmitted signal (by amplitudeor frequency) to transmit over greater distance or, in the event of nodefailure, to by-pass the silent node and reach the next node in sequenceand then maintain as default this new communication pathway and signaltransmission characteristics. In this manner, damaged transceiver nodes,or damaged electrical conducting elements, can be by-passed oraccommodated without substantial loss of data transmission integrity andthe damaged or ineffective elements in the signal communication systemcan be adequately compensated for, as the optimised RF transmissionfrequencies and amplitudes are identified by these automated processes.

Alternatively, the transceiver nodes can optionally be programmed toachieve the same purpose by reducing the bandwidth or frequency of thedata transmissions to reduce noise levels, attenuation and hence powerrequirements to cover the extended transmission distances that may benecessary to traverse as a result of component failures. Failure toreceive confirmation of data receipt from a transceiver node canoptionally also trigger the generation and transmission of a nodefailure report to the data stream to identify at surface that the nodeis not functioning, and optionally to identify the location of thefailed node. This method and process described above is known in the artas ‘adaptive mesh networking’, and alternatively as ‘ad-hoc networking’.

In one embodiment the transceiver nodes operate using an unmodifiedcommercial mesh networking protocol to manage the adaptive networkrouting between nodes. Optionally, the system can use a protocolspecifically adapted to optimise efficiency in a network where the nodesare linearly distributed or axially aligned.

When, as in for example for drill pipes in well, the elongate members(drill string tubulars) are recovered to surface the identified failednodes can then optionally be repaired, or removed and replaced.

Optionally the transceiver nodes can incorporate coding devices adaptedto incorporate such sensor data gathered from the local transceiver intothe signal transmitted by the local transceiver through the signalconductor. Optionally each transceiver node has a code that uniquelyidentifies that transceiver node. Optionally the signal transmitted andreceived by each transceiver node in the assembled string can be thesame, but in some embodiments of the invention, the transmitted signalis optionally modified by some or all of the transceivers nodes as it isrelayed from one transceiver node to another, so the signal received bya transceiver node is not the same as the signal it transmits.

For example, some or all of the transceiver nodes can receive the signalfrom adjacent transceiver nodes and transmit a slightly modified signalincorporating additional data collected at that transceiver node.Typically, this additional data would report on local conditions (e.g.pressure, temperature, salinity, pH, gas concentration, vibration, etc.)at the transceiver node and would also be coded to identify thetransceiver node generating the additional data. In this way, the signalcan be interpreted at the surface to identify local environmentalconditions at each separate transceiver node that recorded a modifiedsignal, so that local conditions can be measured along the length of thestring and not just at the end of the string where traditionally all ofthe sensors are located.

Once each of the transceiver nodes are made up on the string of elongatemembers and run into the well, their relative positions in the stringare fixed, and this allows the physical origin of the data within thewell bore to be tied to the identification (ID) code of the signal. Thelength of each elongate member and the ID code for the transceiver nodeon it are recorded, either manually or electronically, as the assemblyis run in to the well. These positional data are then correlated withthe signal IDs being received at surface to identify the physicallocation of each data transmitted.

Embodiments of the invention permit reconfiguration of the datatransmission pathway either by relocation of transceiver nodes orthrough self-adaptive changes or manual intervention to thetransmissions, to optimise the system performance. For example, if onetransceiver node fails, or if one conductor on one tubular fails, thesystem can be reconfigured or replaced during a full or partial routinerecovery of the bottom hole assembly to surface (a ‘trip’) or betweentrips, to optimise performance.

Typically the signal generator can be a conventional downhole sensoralready incorporated in the string. The Bottom Hole Assembly of atypical drilling system (BHA) is typically provided with suitablesensors, sometimes known as Measurement While Drilling tools, LoggingWhile Drilling Tools, Seismic While Drilling tools, and FormationEvaluation While Drilling tools, and in certain embodiments of theinvention, the apparatus transmits measurement data generated from oneor more of the BHA sensors.

In other embodiments of the invention the signal comprises data from asensor incorporated in the string, optionally incorporated in a signaltransceiver node. In certain embodiments, the signal generator cancomprise a conventional third party signal generator that can beincorporated within a tool in the string (e.g. in the BHA) or can be outwith the string, elsewhere in the well. At surface, a dedicatedtransceiver node, typically not on the string, can typically pick up thesignal from the transceiver node on the tubular closest to surface andrelay it to a computer or data collection station containing software todecode, segregate, and display the various data variables that have beencarried up the string.

In addition to relaying data from various sections of the well tosurface, data can be sent from surface to node locations in the stringas commands to control devices in the string. These commands could be toswitch off or on specific sensors, change sample rates or resolution ofsensors, and also, commands to initiate change of state in mechanical,hydraulic, or electrical tools within the string. These commands fromsurface can also be used to control the data transmissioncharacteristics of the system such as data rate and data frequency.

The tubular can typically comprise a drilling tubular such as drillpipe, and the string of tubulars can typically have a drill bit, andoptionally a bottom hole assembly at the lower end. In thisspecification, the upper end of the drill string can typically beconsidered to be the end nearest the wellhead at the surface, and thelower end of the drill string can typically be considered to be the endfurthest from the wellhead and closest to the location where the bit iscutting into the rock formation. Usually the lower end is physicallylower than the upper end, but in horizontal drilling this is notnecessarily the case, and references to upper and lower ends should beconstrued accordingly.

In one embodiment the apparatus can incorporate an energy generator todeliver energy to the transceiver nodes, typically formed as part of thetransceiver node. In certain embodiments with energy generators, aportion of the transceiver sleeve is free to rotate about the pipe whilethe remainder is rigidly clamped to the pipe. As the pipe is rotated asin the normal process of drilling, the rotating portion of the sleeveremains stationary relative to the well bore due to friction of contactwhile the remainder of the clamp rotates with the pipe to which it isattached.

In such embodiments, a energy generator can be incorporated in thetransceiver converting the kinetic energy generated by the relativerotation of the two sections of the transceiver collar or tubular intoelectrical energy to power the transceiver in a similar manner to adynamo or alternator, the stator of the generator device being imbeddedin the rotating sleeve, and rotor in the portion that is rigidly clampedto the pipe or into the pipe surface itself, or vice versa. To providecontinuous power during non-rotational periods of operation, theelectrical energy generated as a result of the normal drill stringrotation in the wellbore is typically used to maintain the charge ofrechargeable battery cells within the transceiver.

In another embodiment the generator can comprise solid-state electromechanical or magneto-mechanical materials or devices, such as apiezoelectric material that generates electrical energy in response totension, compression or vibration, or a magnetostrictive material thatgenerates energy in response to mechanical loads. In such embodimentsthe device will be secured within the transceiver node unit such thatthe mechanical loading experienced by the transceiver unit during normalwell operations transfers the tension, or compression, or vibrationrequired by these devices to produce an electrical energy into thegenerator component. To provide continuous power during non-rotationalperiods of operation, the electrical energy generated maintains thecharge of rechargeable battery cells within the transceiver.

Optionally the transceiver nodes can have mechanical functions such astubular centralisers or friction-reduction stabilisers. Existingcomponents of the string can optionally be modified to be part of thedata transmission pathway.

Potentially many different specifications of tubular can be converted byapplying the signal conductors and transceiver nodes as retrospectivemodifications. Tubulars according to the invention that mayconventionally have a protective coating to the internal diameter cantypically be recoated and repaired without detriment to the datatransmission effectiveness.

Drill pipe mechanical connections at the end termini of the tubulars aretypically not part of the data network, and so can be designed accordingto the requirements of the physical connection, meeting torque limitsand other parameters without affecting data transmission. Damaged threadon used tubulars can be repaired by re-cutting, reforming, or replacingend connectors without compromising data transmission. In applicationsto oil and gas wells, following the drilling process, operations toconduct reservoir fluids to surface, or pressure support fluids fromsurface to reservoir will typically continue through the life of thewell. For these operations the drilling tubulars are typically replacedwith thinner walled, larger internal diameter tubulars usually referredto as tubing, production tubing or casing. Embodiments of the inventiondescribed previously for drilling applications can be incorporated intothese post-drilling application embodiments in exactly the same way forthe purposes of data and command transmission.

Optionally the signal conductor is located on the outer surface of thetubular and/or on the inner surface of the tubular and/or embeddedwithin the wall of the tubular. The electrical conductor is typicallyfully embedded in the coating or between the abrasion resistant andcoating layers, and is typically sandwiched between them, in order toinsulate it from the tubular and from the environment outside (orinside) the tubular.

The transceiver nodes can optionally incorporate electronic controlcircuitry that controls adaptive mesh network features used to improvesystem redundancy. Embodiments of the invention allow better access todetailed real-time downhole data without recovering (‘tripping’) the BHAback to surface, which can improve safety, increase rate of penetration(ROP), extend life of the BHA by better forecasting of local conditionsliable to damage the bit and drill string, and can also improvepositional accuracy through the reservoir, reducing the need to drillbeyond target. The various aspects of the present invention can bepracticed alone or in combination with one or more of the other aspects,as will be appreciated by those skilled in the relevant arts. Thevarious aspects of the invention can optionally be provided incombination with one or more of the optional features of the otheraspects of the invention.

Also, optional features described in relation to one embodiment cantypically be combined alone or together with other features in differentembodiments of the invention. Various embodiments and aspects of theinvention will now be described in detail with reference to theaccompanying figures. Still other aspects, features, and advantages ofthe present invention are readily apparent from the entire descriptionthereof, including the figures, which illustrates a number of exemplaryembodiments and aspects and implementations. The invention is alsocapable of other and different embodiments and aspects, and its severaldetails can be modified in various respects, all without departing fromthe spirit and scope of the present invention.

Accordingly, the drawings and descriptions are to be regarded asillustrative in nature, and not as restrictive. Furthermore, theterminology and phraseology used herein is solely used for descriptivepurposes and should not be construed as limiting in scope. Language suchas “including”, “comprising”, “having”, “containing” or “involving”, andvariations thereof, is intended to be broad and encompass the subjectmatter listed thereafter, equivalents, and additional subject matter notrecited, and is not intended to exclude other additives, components,integers or steps. Likewise, the term “comprising” is consideredsynonymous with the terms “including” or “containing” for applicablelegal purposes.

Any discussion of documents, acts, materials, devices, articles and thelike is included in the specification solely for the purpose ofproviding a context for the present invention. It is not suggested orrepresented that any or all of these matters formed part of the priorart base or were common general knowledge in the field relevant to thepresent invention.

In this disclosure, whenever a composition, an element or a group ofelements is preceded with the transitional phrase “comprising”, it isunderstood that we also contemplate the same composition, element orgroup of elements with transitional phrases “consisting essentially of”,“consisting”, “selected from the group of consisting of”, “including”,or “is” preceding the recitation of the composition, element or group ofelements and vice versa.

DESCRIPTION OF DRAWINGS

All numerical values in this disclosure are understood as being modifiedby “about”. All singular forms of elements, or any other componentsdescribed herein are understood to include plural forms thereof and viceversa. In the accompanying drawings;

FIG. 1 is a schematic perspective view of a first and second tubularforming a string of tubulars incorporating apparatus according to theinvention;

FIG. 2 is a schematic view of a drill string (not to scale)incorporating the tubulars shown in FIG. 1;

FIG. 3 is a perspective cut away view showing the internal detail of theseparate layers of the tubular shown in FIG. 1;

FIG. 4 a is a perspective cut away view showing the detail of the layersfrom another perspective;

FIG. 4 b is a perspective cut away view showing the detail of the layersof an alternative signal conductor configuration;

FIG. 4 c is a perspective cut away view showing the detail of the layersof a further alternative signal and conductor configuration;

FIG. 5 is a perspective sectional view of a coating layer incorporatinga signal conductor suitable for use in the tubular of FIG. 1.

FIG. 6 a is a schematic perspective of a Transceiver node housing.

FIG. 6 b is a schematic perspective of the Transceiver outline andlocation with respect to the Transceiver node and an adjacent electricalconductor.

Referring now to the drawings, a typical onshore or offshore oil or gaswell as shown in FIG. 2 utilises a drilling apparatus P located above awell head H through which a drill string S is rotated from the surfaceapparatus P. At the downhole end of the string S, a drill bit B on abottom hole assembly (BHA) cuts a hole into the formation, therebyforming the borehole of the well. The string S is made up of sections oftubular drill pipe that are connected end to end by box and pinconnections which can be conventional in the art.

As shown in FIG. 1, each section of tubular T1, T2, etc. in the string Stypically has an enlarged diameter section at the end housing aninternal connection (e.g. a box and pin thread connection at respectiveends). Between the enlarged diameter sections, the nominal outerdiameter of the tubular T1, T2, etc. is typically less than the outerdiameter of the end terminal connector sections. In accordance with theinvention, the reduced diameter central sections between the enlargeddiameter end terminal sections of the tubular T1, T2 are covered atvarious locations around the circumference by a signal conductor, thattypically extends along the length of the reduced diameter portion ofthe tubular T1, and optionally, but not typically extends onto theenlarged diameter end terminal sections, and typically terminates someway short of each end of the tubular T1, T2, etc.

The optional signal conductor in the present embodiment typicallycomprises a multi-layer component that is wrapped or otherwise appliedto the outer surface of the narrower central section of the tubular T1.As best described with reference to FIGS. 3, 4 a, 4 b and 4 c, thenarrow central section 12 of the tubular T1 typically comprises a steeltube having a typical diameter of 4 to 7 inches, although the inventioncan typically be applied to many different specifications of tubular.The outer surface of the central section 12 typically has an insulatingcoating layer applied to it, typically by flame-spray coatingtechniques, for example by HVOF coating (high velocity oxy-fuel coating)or plasma spraying directly on to the outer diameter of the pipe.

These techniques involve spraying the components in fluid form from gunsand nozzles that force the components forming the coating at highvelocities and temperatures through the nozzle of the gun and onto thesurface of the pipe to be coated, resulting in a very high adherence ofthe materials to the substrate of the pipe. Typically, the depositedmaterial forms a state when first deposited which yields electrical andmechanical properties which are different from the normal bulk materialproperties. For materials such as copper and other metals and fornon-metallics such as polymers or ceramics, this creates electricalproperties that can be altered by various degrees of compositional andtopological changes in the sprayed materials and by processes such asthermal annealing post-deposition.

Typically, the coating can be sprayed circumferentially around theentire outer surface of the central section 12 or in discrete axialstrips. In other embodiments, the coating layer can be formed separatelyas a planar flexible sheet and wrapped around the outer surface of thecentral section 12, being fixed in place by adhesive or bonding by othermeans.

On the outer surface of the insulating coating layer, a signal conductor8 is applied. The signal conductor 8 is typically in the form ofmetallic strips, or alternatively metallic sheet or mesh, as shown inthis embodiment. In the present embodiment, the mesh 8 is formed as acylindrical shape and comprises a network of individual strands formedby weaving or braiding individual strands of copper wire or thin coppersheet together to form numerous inter-connections between adjacentstrands. In the present embodiment, approximately 40 to 60 strands ofcopper wire or copper strips are woven in a regular pattern so that eachcopper strip extends helically around the outer circumference of theapplied coating layer. In the present embodiment, approximately half ofthe copper wires or strips extend in a clockwise helix, and the othersextend in an anti-clockwise helix.

Typically, the pitch of the strands in each helix is approximatelysimilar, so that all strands extending in a clockwise helix areparallel, as are those which extend in an anti-clockwise helix.Typically, the anti-clockwise and clockwise helices are set at the samepitch, although in opposite directions, so that the number ofinterconnections made by each wire remains at approximately the sameintensity as the woven signal conductor 8 extends axially along thetubular T1. Typically, the inner coating layer, applied to the outersurface of the tubular, electrically insulates and physically isolatesthe outer surface of the tubular 12 from the signal conductor 8, so thatnone of the metallic strands or wires forming the signal conductor 8come into physical contact with the outer surface of the tubular T1 atany point. Typically, the inner coating layer 10 extends axially alongthe tubular T1 beyond the signal conductor 8, in order to isolate thesignal conductor 8 from the outer surface of the tubular T1.

On the outer surface of the metallic strand 8, the tubular T1 typicallyhas a further, optionally outer-most, layer 4, which is typically formedof a hardwearing material that primarily insulates and isolates thesignal conductor 8 from the external environment surrounding the tubularT1. Typically, the outer layer 4 also extends axially beyond the signalconductor 8, to isolate the signal conductor from the externalenvironment. The outer layer 4 typically comprises a hardened materialthat is typically resistant to abrasion damage by wearing or scoring ofthe material.

Typically, the layer of outer material 4 can be relatively thick orrobust in comparison to the signal conductor 8 to provide a toughdurable outer layer to protect the signal conducting layer againstimpact, wear and erosion. The outer layer can comprise for example,alumina or alumina compounds, with interspersed polymer or resinmaterials, and/or other hard materials that are wear resistant.Typically, the outer layer 4 also incorporates an electrical resistancein order to resist the passage of the electrical signal radially throughthe outer layer 4. Optionally, a further layer of additionalwear-resistant materials such as Tungsten Carbide may be applied to theouter surface of the whole, to provide further mechanical robustness,These outer materials may optionally have electrically-insulatingproperties or electrically conducting properties for improved electricalsignal transmission and electrical shielding.

In typical embodiments, the inner layer can primarily function as anelectrical insulator, and ceramic materials such as Alumina, Zirconia,Silica or similar materials, optionally with interspersed polymer orresin materials can be used in the formation of the inner layer. Othersuitable materials for the inner layer may include polymers or epoxiesor other electrical insulators or non-conductors.

FIG. 4 b shows an alternative similar configuration using axiallyaligned metal strips 14 as a signal conductor in place of the previousmesh configuration.

In certain embodiments, for example, that shown in FIG. 5, the signalconductor can be enclosed within a discrete layer that is typicallyformed separately as a planar sheet and applied as one wrapped layer onto the outer surface of the tubular, or formed as a cylinder and offeredto the tubular T1. FIG. 5 shows an exemplary signal conductor that isenclosed between two flexible planar sheets of plastics material beforebeing wrapped around the coating layer 10. In certain embodiments, theinner coating layer 10 is unnecessary, typically in those embodimentsthat have the encapsulated signal conductor shown in FIG. 5. Optionally,the encapsulated signal conductor can have a hardened or otherwiseabrasion resistant outer surface coating, which may render unnecessarythe separate outer coating 4 shown in FIGS. 3 and 4. Optionally both maybe implemented together.

Referring once again to FIG. 1, each tubular T1, T2, etc. typically hasrespective transceiver nodes C1, C2, etc. The transceiver node C1typically picks up signals transmitted from the sensors associated withthe bottom hole assembly and drill bit B. The signals transmitted by thebottom hole assembly and drill bit B are typically emitted in radiofrequency form, which are picked up by the signal conductor 8 in tubularT1, and received by transceiver node C1 at the top end of tubular T1.The transceiver node C1 then relays the signal from tubular T1 totubular T2, where it is typically picked up by the signal conductor 8 ontubular T2, and relayed to transceiver node C2, although in embodimentswithout signal conductors the signal is relayed direct from onetransceiver node C1 to the next transceiver node C2 (or C3) on thestring, which can be on an adjacent length of tubular T2 or anothernon-adjacent length of tubular T3.

The transceiver nodes can optionally be in direct contact with thesignal conductor 8 in each of the tubulars T, but this is not necessary,and typically the transceiver nodes C1, C2, etc. can wirelessly pick upand optionally amplify the transmitted signals passing along the signalconductor 8 without having a direct physical or electrical connection tothe signal conductor 8.

In certain embodiments, the transceiver nodes C1, C2 can be locatedradially outwardly from the signal conductor 8. In use, the transceivernodes C1, C2 relay the signal from the drill bit to the surface platformP, where it can be interpreted to gather more information about thewellbore conditions at the drill bit B.

Typically, each tubular T1, T2 etc has respective transceiver nodes C1,C2, etc., but this is not necessary, and transceiver nodes C canoptionally be placed on every second, third, fourth, fifth, or sixthtubular T, depending on desired signal strength and power oftransceivers. Optionally each tubular may have placed on it more thanone transceiver node.

Typically, each transceiver node C1, C2 etc. is substantially identicaland can optionally relay the same signal that it receives, but incertain embodiments of the invention, each transceiver node C1, C2 etc.has a unique identifying electronic code which is encoded by electroniccomponents in the transceiver node into the received code, and which isintegrated into the code that is transmitted. In addition, transceivernodes C1, C2 etc. can optionally incorporate sensors that monitor localconditions at the position of the transceivers, and can also encode thisin the signal that is transmitted from each respective transceiver nodealong with the unique identification code of that transceiver node, Inone embodiment of a transceiver node shown in FIG. 6 a the transceivernode can incorporate a collar extending around the circumference of thetubular T.

The collar can have a component fixed to the tubular F, but canoptionally incorporate an additional sleeve section S which is free torotate around the axis of the tubular. The rotor and stator elements ofa dynamo generator can be incorporated into the transceiver nodeassembly with one being imbedded in the clamped section F and the otherin the rotating sleeve S. As the tubular is rotated as part of normaldrilling operations, the clamped section will turn with the tubular andthe sleeve section will remain rotationally static relative to thewellbore. The relative rotation of the rotor and stator form an energygenerator to power the transceiver, and typically converts the kineticenergy generated by the relative rotation of the transceiver node sleeveand the tubular into electrical or potential energy to power thetransceiver. This electrical energy generated as a result of the normaldrill string rotation in the wellbore is typically used to maintain thecharge of rechargeable battery cells within the transceiver node.

In another embodiment the generator can comprise solid-stateelectromechanical or magneto-mechanical materials or devices, such as apiezo electric material that generates electrical energy in response totension, compression or vibration, or a magnetostrictive material thatgenerates energy in response to mechanical loads. In such embodimentsthe device will be secured within the transceiver unit such that themechanical loading experienced by the transceiver unit during normalwell operations transfers the tension, or compression, or vibrationrequired by these devices to produce an electrical current into thegenerator component. The piezoelectric generator requires no movingparts, and can be incorporated entirely within either a rigidly clampedsection of the transceiver node housing, or alternatively within therotating sleeve component if present. To provide continuous power duringnon-rotational periods of operation, the electrical energy generatedmaintains the charge of rechargeable battery cells within thetransceiver.

In one embodiment of the transceiver node shown schematically in FIG. 6b, a RF transceiver Tn detail is shown in close proximity to an adjacentelectrical conductor E each housed on the same elongate member. In thisembodiment, to optimise the effectiveness of the RF transmissions withthe allowable radial clearances of the transceiver node housing, the RFtransceiver is shown laid onto the circumference of the tubular. In thisembodiment there exists no direct electrical connection between thetransceiver node and the electrical conductor.

1. Apparatus for downhole transmission and reception of data in an oilor gas well comprising a downhole signal transceiver adapted to receivedata from a signal generator and transmit the signal through the welland an elongate member with an axis, located in the wellbore; wherein:the signal is transmitted by the transceiver, predominantly axiallyalong the elongate member, there being at least two down holetransceivers, said transceivers being linked in series as nodes alongelongate members; the signal presented at the transceiver nodes and atthe elongate members is a radio frequency (RF) signal and the elongatemembers incorporate a signal conductor comprising a conductive element;the signal conductor is optimised in its effectiveness of transmittingRF signals by variations to its electrical impedance, through changes toits material composition or morphology and/or changes to its physicalarrangements such as width, thickness, length and separation fromadjacent surfaces, which influence its electrical impedance andelectrical resistance and efficiency at carrying RF signals. 2.(canceled)
 3. Apparatus according to claim 1 wherein said signalstransmitted comprise signals from the, or each transceiver, and one ormore sensors in the well.
 4. (canceled)
 5. (canceled)
 6. (canceled) 7.Apparatus according to claim 1 wherein the signal conductor iselectrically insulated from the environment by resting withinelectrically-insulating materials optimised for the RF signals beingtransmitted.
 8. Apparatus according to claim 7 wherein, the electricalinsulating materials are coated with further electrically conductinglayers.
 9. (canceled)
 10. (canceled)
 11. (canceled)
 12. Apparatusaccording to claim 1 wherein the signal conductors are mounted on thesurface of the elongate members.
 13. (canceled)
 14. Apparatus accordingto claim 1 wherein the signal conductors have a lower electricaltransmission loss to transmission of the signal than the elongate memberor the surrounding fluid medium, thereby increasing the efficiency oftransmission between transceivers.
 15. (canceled)
 16. Apparatusaccording to claim 1 wherein the signal conductor is incorporated withinthe wall of the tubular such that the signal conductor extends axiallyalong the elongate member, as well as circumferentially, so that thesignal carried by the signal conductor is transmitted along theconductor and along the axial length of the elongate member. 17.(canceled)
 18. (canceled)
 19. (canceled)
 20. Apparatus according toclaim 1 wherein the signal conductor comprises one or moreaxially-aligned strips.
 21. Apparatus according to claim 20 wherein morethan one axial strip is provided and adjacent axially-aligned strips arepositioned be parallel to one another, so that they extend parallel tothe axis along the length of the elongate member.
 22. Apparatusaccording to claim 1 wherein the signal conductor is of uniformdimensions of width and thickness along the length of the signalconductor.
 23. (canceled)
 24. (canceled)
 25. Apparatus according toclaim 31 wherein the signal pathway transmits large amounts of databi-directionally along the elongate structure as exemplified byradio-frequency transmissions up to the Megahertz and Gigahertz rangeand to send commands to transducers and actuators placed along theelongate structure to change their status or mode of operation. 26.Apparatus according to claim 31, wherein the pathway is formed usingflame spray techniques to achieve a robust structure, as applied to theoutside surfaces or inside surfaces of the elongate structure. 27.(canceled)
 28. Apparatus according to claim 31 wherein electricalconductors with non-uniform dimensions are provided to optimise thetransmission and reception of the wirelessly-transmitted signals. 29.Apparatus according to claim 31 further comprising friction-reducers andannular ring spacers to house RF transceivers and transceiverelectronics, sensors, power supplies and ancillary electronic circuitry.30. Apparatus according to claim 29 wherein said friction-reducers andannular ring spacers are formed as housings to incorporate an energyharvester to supply energy to the electronic systems and signaltransmissions.
 31. Apparatus comprising a wireless network formed by theinteraction of transceiver nodes and electrical conductors placed alongelongate member surfaces combined with an embedded capability to alterthe signal transmission pathways that are used at any one time in orderto optimise the signal transmission data rates or energy requirements.32. Apparatus according to claim 31 wherein transceiver nodes are placedalong the elongate member that possess their own identification. 33.Apparatus according to claim 32 wherein transceiver nodes that containembedded sensors are provided to allow data to be gathered from multiplepoints along the elongate members.
 34. Apparatus according to claim 32wherein said transceiver nodes that contain RF transceivers arepositioned conformal to the tubular, so as to optimise the transmittedand received signals within the radial clearance confinements of thenode housing.
 35. A method of downhole transmission and reception ofdata in an oil or gas well comprising providing a downhole signaltransceiver adapted to receive data from a signal generator and transmitthe signal through the well and providing an elongate member with anaxis, extending through the wellbore; and transmitting the signal fromthe transceiver along the elongate member via a wireless network formedby the interaction of transceiver nodes and electrical conductors placedalong the elongate member surfaces combined with an embedded capabilityto alter the signal transmission pathways that are used at any one timein order to optimise the signal transmission data rates or energyrequirements.